Suspension-bed hydrocracking technology is an important process in refining heavy oil to light oil. The primary difference between a suspension-bed reactor and a conventional hydrocracking fixed-bed reactor is that the catalyst in the suspension bed reactor is flowing. Currently, the commonly used hot-wall reactor for suspension-bed hydrocracking usually employs a hollow internal part-free barrel reactor. A mixture of raw oil material, hydrogen and catalyst enters the reactor from the bottom, flows upward, and flows out from the top of the reactor. However, since the wall temperature of the hot-wall reactor for suspension-bed hydrocracking is high, reaction materials inside thereof easily got coked on the side wall of the reactor, which affects the fluidity of the material inside the reactor. The process of the reaction is further impacted due to the uncertainty of catalyst is flowing and makes the operation of the reactor unstable.
Flow conditions of the gas-liquid-solid three-phases in the suspension reactor are an important indicator of the quality of reaction, which directly affects the conversion rate, the quality of the product and the running period. Because of the action of the wall effect, the fluid linear velocity of the reactor axis is relatively high, and the fluid linear velocity near the wall surface is relatively low, therefore the gas entering the reactor is not evenly distributed. Thus, the big bubble rises quickly in the process, and a short circuit occurs in the gas rising process. The occurrence of these two phenomena results in severe fluid back-mixing within the reactor, weakening of the interphase mass transfer and weakening of the heat transfer effect, which make it difficult to make uniform temperature distribution within the reactor, and lead to increased coke yield, decreased conversion rate, and seriously affected operational life of the reactor. As the suspension-bed reactor has higher requirements for the uniformity of the mixed raw materials, hydrogen and catalyst, it is required to fully mix raw materials, hydrogen gas and catalyst so that the hydrogen and the raw materials can fully react on the surface of the catalyst and the hydrogen can be quickly dissolved to the required raw materials, which make the hydrogenation occur. Therefore, the requirements of the mixing process are high. In addition, since the temperature of the reactor wall is high, the materials may easily aggregate and coke on the inner wall and the hydrogen may easily corrode the reactor wall, thus material requirements of the reactor cylinder are high.
For example, a Chinese patent, CN204051658U, discloses a hydrogenation reactor which comprises a reactor body and a support base. The reactor body comprises a vertically arranged cylinder body, and an upper seal head connected to the top of the cylinder and a lower seal head connected to the bottom of the cylinder. The upper seal head is provided with a discharge pipe, and the lower sealing head is provided with a feed pipe. Two connecting hydrogen pipes are vertically arranged at intervals on the side wall of the cylinder. Each of the cylinder body and the upper and lower head structure comprises in a sequence from outside to inside, a first metal shell, a first stainless steel corrosion-resistant layer, a first thermal insulating liner and a first steel liner. The first stainless steel anti-corrosion layer is arranged by overlay welding on the inner side wall of the first metal shell. The hydrogenation reactor is a cold-wall structure. The working temperature of the metal shell is much lower than the maximum working temperature limit of the material. A well-established chromium-molybdenum steel hydrogen corrosion resistant material can meet the working requirements. The inner wall of the metal shell is not provided with an anchoring nail, but is provided with a stainless steel anti-corrosion layer by overlay welding, and is provided with a steel liner on the inner sidewall of the thermal liner to avoid thermal liner fouling caused by reaction medium. Thus, this design meet the requirement of the hydrogen and hydrogen sulfide corrosion resistance, can break through the working temperature limit of the existing hydrogen corrosion resistant steel, provide the resistance to hydrogen and hydrogen sulfide and other medium corrosion. However, in the cold-wall hydrogenation reactor mentioned above, cold hydrogen gas can only enter the steel liner through limited number of inlets, which allows only limited amount of materials in the steel liner to contact the cold hydrogen, while the materials far away from the air inlet cannot be sufficiently mixed with cold hydrogen. As a result, the three-phase materials in the reactor is not mixed uniformly, the amount of cold hydrogen in different positions are different and temperature of the materials are different, which further leads to coking caused by local hot spots of the materials and impaired fluidity of the materials and the catalyst. The flowing of the catalyst in the reactor cannot be ensured, and the reaction efficiency is therefore low.